NFPA Code 409

Standard on AircraftHangars

NFPA Codes

NFPA Code 409

NFPA 409, Standard on Aircraft Hangars, contains the minimum
requirements for the proper construction of aircraft hangars
and protection of aircraft hangars from fire. Intended to
provide protection to both life and property from fire, this
standard applies to buildings or structures used for aircraft
storage, maintenance, or related activities. Other uses within
an aircraft hangar, such as offices or tool storage, should be
protected in accordance with applicable NFPA Standards. Protection
systems include overhead deluge foam water sprinklers, or overhead
closed head water sprinklers combined with supplementary low-level,
low or high expansion foam systems. Under certain conditions,
overhead closed head foam systems are also permitted.

NFPA 409 has specific requirements for acceptance testing of individual
systems, since hangars usually have multiple, large flow foam
conditions. Full flow water testing of each deluge system must be
performed as a means to check sprinkler distribution and to ensure
against pipe clogging by foreign matter. The smallest single foam system
must be discharged using foam concentrate. The maximum number of systems
expected to operate must be simultaneously discharged with foam. All
proportioners must be tested using foam. Supplementary and low level foam
systems must also be tested to assure accurate proportioning. Special
provisions are provided for flowing overhead and supplementary low-level
systems simultaneously.

Additionally, NFPA 409 requires testing of fire protection systems in
aircraft hangars to be performed in accordance NFPA 25 Standard for
the Inspection, Test and Maintenance of Water-Based Fire Protection
Systems. The NFPA 25 requirements include monthly inspections and annual
testing of proportioning and other equipment. Alternate methods to match
full flow conditions are allowed where there are conflicts with local
regulations. Discharge time and patterns are to be noted, along with key
pressure readings and the foam concentration.